Adding special characters to numbers not to text

[Tei28204474v2l3]

Good Day Pros, 

               I am reaching out today as I have a situation where I have a text box " % Body Fat ".  I am looking for a way that if a number is entered in it will add the % sign to the backside of the number. If the text W/S is entered, it will just be W/S. Is it possible to do this?

[PDF Automation Station]

Enter the following as a custom format script:

if(!isNaN(event.value))
{event.value=event.value+"%"}